A former CSP Trooper, I was issued one, NIB, in 1980. Department regulations stated your duty gun had to have a dark finish, no nickel or SS guns. You had the option of using your own gun as long as it was a Colt or S&W, 4 or 6 inch barrel, 6 shots, and chambered for .357 mag. Checked by the armorer at each qualification.
The "blackened" finish was not as durable as real blueing, and it showed on guys guns who did a lot of holster work. I never cared for the balance of the 66 when D/A shooting, and replaced it with one of the first 586's that came out. We could have bought our 66's for something like $250, but I didn't. We also could have bought a new Beretta 92 in a one time deal, at something like two hundred bucks and change when we switched out from revolvers in 1985(?). I regret not doing that buy.
Larry